Natural history of asymptomatic carotid artery stenosis.

The prevalence of carotid artery stenosis 50% or greater increases from about 1% in people aged 50 to 59 to about 10% in people older than 70. Although carotid stenosis accounts for about 10% of ischemic strokes, only a minority of patients with carotid stenosis will have a stroke. The annual risk of ipsilateral ischemic stroke is relatively low, ranging from 1.0 to 3.8% and is about half of that of any stroke. There is a relatively weak relationship between carotid stenosis severity and risk of ipsilateral stroke. In addition to stenosis severity, carotid plaque composition, which can be evaluated by several noninvasive imaging methods, may be an independent risk factor for stroke. There are few data supporting the use of hemodynamic impairment assessment to predict stroke risk. Nonstroke vascular events are about twice as likely in patients with carotid bruits compared with those without. Patients with asymptomatic carotid stenosis have a particularly high risk of cardiac events (about 3.5% per year). Therefore, the most important part of the management of patients with carotid stenosis is optimization of medical therapy. Much remains to be done to identify patients at particularly high risk of ipsilateral stroke, for whom carotid endarterectomy may be necessary in addition to medical therapy.